Melt most of the butter in a large, heavy-based saucepan over a moderate heat. Sauté the onion for 4-5 minutes, stirring occasionally, until softened. Add all the sweetcorn save for a small handful (for garnishing) and stock and bring to the boil.
Reduce to a simmer and cook gently for 15 minutes. Remove from the heat and purée with a stick blender until smooth. Transfer back to the saucepan and adjust the seasoning as necessary.
Stir in the cream and some of the Cheddar, saving some for the garnish. Melt the remaining butter in a frying pan over a moderate-high heat, then sauté the chopped bacon for 2-3 minutes, tossing and stirring occasionally. Make sure the soup is hot, then ladle into mugs.
Garnish with tablespoons of the bacon, Cheddar and the reserved sweetcorn. Serve immediately.
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